Harmful sewage continues to pollute Kailua Bay despite increased scrutiny
As rains fell hard this week, the treated sewage that flowed into the ocean from the city’s regional wastewater plant in Kailua was found to have abnormally high levels of bacteria, posing a health risk to nearby beachgoers.
Now, with more heavy rains headed toward Oʻahu, officials are trying to determine exactly why this latest sewage incident coincided with a storm.
The Kailua Wastewater Treatment Plant, on the island’s wettest side, already receives plenty of state and federal scrutiny following past cases of unacceptably high bacteria in the water amid heavy storms. That includes mandated equipment upgrades so the aging plant runs more reliably, with fewer malfunctions, and kills harmful bacteria more effectively.
Still, the plant remains vulnerable to sewage treatment problems caused by heavy storm flows, according to City Environmental Services Deputy Director Michael O’Keefe. That’s despite the addition of a giant Kailua to Kāneʻohe gravity sewer tunnel that since 2018 has been storing the excess millions of gallons of rainwater that flood the sewer system on the Windward side of the island.
Storms can affect the plant in a number of ways, including washing away the biological agents used to clean the sewage, O’Keefe said. Sometimes, he added, it’s not clear how exactly the rain caused the plant to fail — or if it was even a factor at all.
“These treatment plants are very complex and anything could have gone wrong,” O’Keefe said Tuesday of the latest incident as his division awaited confirmation of test results showing elevated levels of enterococci.
The bacteria can be harmful to humans, according to the National Institutes of Health. On Monday, crews posted signs warning swimmers to stay out of the water near where treated sewage is released into Kailua Bay.
The city will conduct a more intensive investigation into what might have caused the levels to rise above what state and federal regulators consider safe, O’Keefe added, with findings expected in five days or so.
In 2023, the state Department of Health fined the City and County of Honolulu more than $400,000 for excess levels of bacteria in treated sewage over 13 days in April and May of that year. On a couple of those days the levels were six times higher than the state limit, a clear violation of the city’s permit with the Hawaiʻi Department of Health.
At the time, the city pointed out that the violations had occurred during heavy rains.
A Corroding Tower
The U.S. Environmental Protection Agency has issued two consent decrees in recent years requiring the city to improve how it runs the Kailua plant and make millions of dollars in upgrades. While those repairs are underway, none are complete.
Under the EPA’s September 2023 order, the city was compelled to upgrade one of two “bio-towers” at the plant that is corroded and occasionally breaks down. In those towers, sewage is exposed to biological agents that help eliminate bacteria as it trickles through, O’Keefe said, but the process depends on a sprinkler-like arm to properly distribute the wastewater through the interior.
On at least one occasion, he added, a spike in bacteria levels occurred when that aging arm broke down. It’s working OK now, O’Keefe said, but state and federal officials have required that the city overhaul that and other old equipment in the tower.
The bio-tower rehabilitation project is slated to cost about $42 million, according to Environmental Services Department spokesman Markus Owens. O’Keefe estimated it should be done within four years.
Separately, the city is reinstalling a disinfection process using ultraviolet light at the Kailua plant to more effectively kill off lingering bacteria. That UV system existed at the plant up until 2009, but heavy water flows flooded the channel and damaged electronics on top of the UV lights.
The UV system is currently slated to cost $11 million, although an EPA report in 2017 estimated that it should only cost around $500,000. Officials have said it won’t be at risk of damage from flooding, and O’Keefe said on Tuesday it should be completed by the end of the year.
More Testing, Rains Ahead
The samples were collected Monday from inside the plant before the treated sewage was released into the ocean. That sewage effluent is released at a point about 5,000 feet offshore in Kailua Bay near the Mōkapu Peninsula.
The city in a press release Tuesday did not specify to what extent the enterococci samples exceeded the state’s limit. It did note that the levels collected the previous day were considered safe, and that it would continue to test the levels in the coming days.
“While the Department of Environmental Services investigates the cause of the exceedance,” the release stated, “we are aware the plant recently experienced high flows due to heavy rains.”
More such heavy rains are forecast to arrive on Oʻahu as early as Wednesday night.
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Civil Beat Reporter Ben Angarone contributed to this story.
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This story was originally published by Honolulu Civil Beat and distributed through a partnership with The Associated Press.